Split Segments by Endpoint Proximity

Detects cases in which segments should be split to establish appropriate topology, and splits them. Specifically, it looks for segment endpoints intersecting (or within a tolerance of) another segment. It then splits the intersected segment at the point where the endpoint of the other segment breaks it.

splitsegments(rivers, tolerance = NULL, splitthese = NULL,
  splitthemat = NULL, one2one = FALSE, append = FALSE)

Arguments

rivers

The river network object to use
tolerance

The spatial snapping tolerance to use for detecting intersection. If a NULL value is used (default), it will default to the tolerance that was used in river network creation in line2network.
splitthese

An optional vector of target segments to split. If this argument is used, only these segments will be split. If the default (NULL) is accepted, all segments will be used.
splitthemat

An optional vector of segments (endpoints) to use for splitting. If this argument is used, segments will only be split at the endpoints of these segments. If the default (NULL) is accepted, all segments will be used.
one2one

Logical, indicating a one-to-one correspondence between arguments splitthese and splitthemat. Defaults to FALSE,
append

Logical, indicating how to organize the output river network. If TRUE, appends newly-created segments to the end of $lines, rather than retaining original line ordering. This may be useful in retaining original line ID. Defaults to FALSE.

Value

A new, updated river network object

Note

This function is called within cleanup, which is recommended in most cases.

See also

line2network

Examples

data(Koyukuk1)
topologydots(rivers=Koyukuk1)
# Segments 7, 8, 13, and 16 need to be split so topologies will work.  
# Since endpoints are not in the same place, they are not detected as 
# being connected.
plot(x=Koyukuk1)

Koyukuk1split <- splitsegments(rivers=Koyukuk1)
#> Note: any point data already using the input river network must be re-transformed to river coordinates using xy2segvert() or ptshp2segvert().
topologydots(rivers=Koyukuk1split)
plot(x=Koyukuk1split)

# if only segment 17 were to be split in three places
plot(x=splitsegments(rivers=Koyukuk1, splitthese=c(7,7,7),
        splitthemat=c(14,5,12)))
#> Note: any point data already using the input river network must be re-transformed to river coordinates using xy2segvert() or ptshp2segvert().

# if only segment 16 were to be split, showing behavior of append=
plot(x=splitsegments(rivers=Koyukuk1, splitthese=c(7,7,7),
        splitthemat=c(14,5,12), append=TRUE))
#> Note: any point data already using the input river network must be re-transformed to river coordinates using xy2segvert() or ptshp2segvert().